Process for preparation of organoboron compounds



, wholly unobtainable.

United States Patent 3,106,560 PRGCESS FOR PREPARATION OF ORGAN 0- BORON CDMPOUNDS Eugene C. Ashby, Walter E. Foster, Jesse R. Maugham, and Tillmon H. Pearson, Baton Rouge, La, assignors to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Original application Apr. 10, 1957, Ser. No. 651,797, now Patent No. 2,961,443, dated Nov. 22, 1960. Divided and this application Oct. 8, 1959, Ser. No. 848,886

5 Claims. (Cl. 260-290) This invention relates to the preparation of organic compounds of boron.

Certain organic derivatives of boron have been synthesized by the reaction between a dialkyl or diaryl derivative of mercury or zinc and a boron halide. For example, the carefully controlled reaction between dimethyl zinc and boron trichloride was used by E. Wiberg and W. Ruschmann, Berichte, 70, 1583 (1937), to prepare the methyl dichloroborane and the dimethyl chloroborane. However, these compounds are unstable and readily disproportionate to trimethyl borane and boron trichloride. These and certain other organic derivatives of boron are more satisfactorily synthesized by the employment of a Grignard reagent and boron halides re acted as their ether complexes. In this manner both the trialkyl and triaryl compounds have been prepared. The alkyl derivatives, for example, are prepared by the methods disclosed by H. C. Brown and R. B. Johannesen, Journal of the American Chemical Society, 75, 19 (1953), and the aryl derivatives by procedures exemplified by the work of E. Krause and H. Polack, Berichte, 59, 777 (1926). Thus, these and other methods have been utilized by workers in the field to prepare a variety of organo boron compounds, some of which are more diflicultly obtainable than others, such as the mono-organo derivatives and the mixed organo derivatives. However, the art propounds no uniformly applicable method for the preparation of these diflicultly obtainable organic derivatives of boron. Thus, in following the procedures disclosed in the prior art, there will be synthesized compounds, in many instances, which are unstable even at extremely low temperatures, and which in order to maintain stability must be further reacted in order to formulate the compound into a suitable state for convenient isolation or storage. A clear illustration involves the mixed alkyls of boron, such as dirnethyl ethyl boron, which disproportionate very readily even at temperatures in the region of 20 C., according to the work of T. D. Parsons and D. M. Ritter, Journal of the American Chemical Society, 76, 1710 1954). Thus, the inherent tendency of boron compounds to disproportionate makes it extremely difficult, using any of the methods in the art, to obtain in a simple and economical manner con trolled organo substitution of boron.

It is, therefore, an object of this invention to prep-are difficultly obtainable organic compounds of boron. It is, additionally, an object of this invention to prepare organic compounds of boron Which heretofore have been A still further object is the preparation of organo boron compounds in a simple and economical manner suitable for commercial adaptability.

In accordance with these objects and others which shall appear hereinafter, a stable organometallic of the type R M wherein R is a hydrocarbon radial, M is any metal which will form a stable organometallic, and y is an integer equal to the valence of M, is reacted with an amine complex of a boron compound having the general formula wherein R is a hydrocarbon radical, X is a halide or alcohol residue, A is any primary, secondary or tertiary amine or ammonia, and a is an integer having a value between 0 and 3. In a preferred embodiment of this invention, a tertiary amine complex of a boron halide is reacted with an alkali metal alkyne, such as, for example, the reaction between the pyridine complex of boron trifluoride and sodium acetylide, as more fully illustrated in the following example. In this and other examples which occur below, all parts and percentages are by weight.

Example 1 Into' a reaction flask provided with means for heating, cooling, stirring, and continuous addition was added 11 parts of boron trifiuoride in 200 parts of pyridine. To this mixture was added in a continuous steady stream 24 parts of sodium acetylide in 200 parts of xylene over a 15 minute period while maintaining the reaction temperarture at 0 C. After completion of this addition the reaction mixture was warmed to 25 C. whereupon the mixture turned purple, some solid appearing in the purple solution. This solid was separated from the reaction mixture in a dry box by vacuum filtration. The solid appeared purple, but when completely dry, turned a light tan color. Further identification revealed the solid to be sodium fluoride. The purple filtrate amounting to about 450 parts was distilled through a glass helix packed column so as to remove the pyridine. Upon completion of the distillation, a purple solid was deposited in the reaction container. This solid was vacuum filtered and recrystallized in acetone water to produce colorless needles having a melting point of 153 C. (plus or minus 0.5 C.) and thereafter dried in a dry box. The desired triethynyl boron pyridine product was obtained in a percent yield.

In the stable organometallic compounds employed in the process of this invention as illustrated hereinabove by the formula R M, R is as defined hereinbefore and, more specifically, is a lower hydrocarbon radical, that is, one containing between about 1 to 10 carbon atoms, preferably lower alkyl and akynyl radicals; M is any metal which will form a stable organometalllc, preferably, those metals selected from the groups IA, II-A, II-B, IIIA, within which the metals sodium, lithium, potassium, magnesium, calcium, zinc, mercury, boron and aluminum are especially preferred for employment in the process of this invention; and, furthermore, y is an integer having a value as defined hereinbefore. Thus, the radical R can be alkyl radicals, such as, for example, methyl, benzyl, isopropyl, hexyl, l-rnethyl octyl, decyl, hexadecyl; aryl radicals, such as, phenyl, tolyl, naphthyl, 4-anthryl, phenanthryl; alkenyl radicals, such as, l-propenyl, l-butenyl, 3-methyl-6-hexyl-'1-octenyl; alkynyl radicals, such as, ethynyl, l-butyny-l, l-hexynyl, 3,3-dimethyl-l-butynyl, 1-

butene-3-ynyl; cycloalkyl radicals, such as, cyclopentyl, cyclohexyl, cycloheptyl; cycloalkenyl radicals, such as, 1,3- cyclohexadienyl, cyclopentenyl, and the like. Furthermore, other metals than those enumerated hereinbefore can be employed as the metallic substituent in the stable organometallics employed as a reactant in the process of this invention, such as, for example, rubidium, cesium, berium, scandium, zirconium, vanadium, chromium, cobalt, palladium, nickel, copper, silver, mercury, gallium, indium, silicon, lead, tin, bismuth and the like.

In the boron compound represented hereinabove by the general formula a is as defined hereinbefore; the radical R is as defined for the radical R hereinbefore, but may or may not be the same radical within the definitive group. X is a halide or alcohol residue as defined hereinbefore. When X is a halide, it is preferred to employ chlorine or fluorine. When X is an alcohol residue, it is preferred to employ alcohol residues containing between about 1 to 10 carbon atoms, said residues being selected from the groups alkoxy or aryloxy, such as methox ethoxy, butoxy, isopropoxy, phenoxy, methoxy benzene, isopropoxy benzene and the like. However, it is not intended that the alcohol residues be limited purely to alkoxy and aryloxy. Certain conjugated alcohol residues such as a-lkenes or cycloalkene alcohol residues, as for example, 1-oxy-2-butene, or 1-oxy-1,3- cyclopentadiene may additionally be employed. The amine substituent represented by A is as defined hereinbefore. Thus, ammonia and any primary, secondary or tertiary amine, wherein the residues replacing the amine hydrogen tare hydrocarbon residues, may be employed. Therefore, the hydrocarbon residue of the amine can be alkyl, cycloalkyl, aryl or a mixture thereof; furthermore, heterocyclic amines are successfully utilized in the process of this invention. Typical, but non-limiting, examples of primary amines include alkyl amines, such as the homologous methyl, ethyl, propyl, buty-l, amyl, hexyl amines and the like, up to and including amines having about 10 carbon atoms in the hydrocarbon chain. Additionally, branched chain monoalkyl amines such as isobutyl amine, 3-amino-4-methyl pentane, l-amino propane, Z-amino butane and the like can also be employed. Specific, but non-limiting, examples of primary amines containing hydrocarbon residues consisting of aryl groups include 111-, and p-amino diphenyl methane, phenyl amine, benzyl amine, naphthyl amine, 0-, m-, and p-ethyl aniline, pisobutyl aniline, p-isopropyl aniline and the like. Examples of secondary amines which can be used include dialkyl amines such as diethyl amine, dipropyl amine, dibutyl amine, Z-methyl amino butane, 2-ethyl amino butane and the like. Furthermore, mixed aryl-alkyl secondary amines can be employed such as phenylethyl amine, benzylmethyl amine and the like. Dialkyl secondary amines such as diphenyl amine, dibenzyl amine, dinaphthyl amine and the like can also be employed. Additionally, cycloalkyl amino compounds may be employed in the process of this invention and typical examples of such cycloalkyl amines are cyclohexyl amine, N-butyl cyclohexy-l amine, N-ethyl cyclohexyl amine, and the like. Also, tertiary amines may be employed in the process of this invention, such as trialkyl tertiary amines like the homologous methyl, ethyl, propyl, butyl, pentyl, hexyl amines and the like. Further, branch chain tertiary amines can be used such as triisopropyl amine, di-tert-butyl methyl amine, and the like. Mixed alkyl-aryl tertiary amines are employed in some instances and typical examples include methyl diphenyl amine, diethyl phenyl amine, cyclohexyl phenyl methylarnine and the like. Heterocyclic tertiary amines can be utilized in the process of this invention and typical, but non-limiting, examples include heterocyclic amines such as pyridine and the homologs thereof, quinoline, piperidine, acridine, isoquinoline and the like.

The reaction occurring in Example I may be depicted by the following formula BF -py1'idine+ 3NaCzCH- B (CE CH) -pyridine+3NaF However, attempted analogous procedures employing identical reaction conditions with the exception that the BF reactant was reacted as an etherate complex, gave negative results as illustrated by the following example.

Example [I The process of Example I is followed with the exception that 11 parts of boron triiluoride in 200 parts of absolute ether is utilized. Immediately upon contact of the BF etherate with the sodium acetylide, a dark reaction mass begins to form. Upon completion of the addition, the reaction mixture is a completely blackened polymerization product. Analysis showed no trace of any acetylenic product. Similar results were obtained by following the process of Example I utilizing BF complexed with other ethers such as diglyme, diethyl ether, tetrahydrofuran and the like. Further, negative results were obtained when BF in an uncomplexed state was reacted in a hydrocarbon medium such as benzene, hexane, toluene, ethane, naphthalene and the like.

Furthermore, an attempt was made to prepare triethynyl boron by reversing the addition of the reagents, that is, boron trifiuoride in ether solution was added to excess sodium acetylide at 70 C. In this reaction a minimum of black polymerization product was noticed and a substantial yield of sodium tetraethynyl borate and sodium finoro borate was produced. However, no triethynyl boron etherate was present. The reaction is represented by the following formula Thus, by reacting stable organometallics with boron compounds of the type defined hereinbefore, stable amine complexed organo boron compounds as more fully illustrated in the following general formula are produced,

wherein R and R are the same or different organic radicals as defined hereinbefore and X is an alcohol residue or halide as defined hereinbefore; a is an integer from 0 to 2; b is an integer of 1 to 3; and c is an integer having a value from 0 to 2; a-l-b-l-c being equal to no more than 3. Typical, but non-limiting, examples of the compounds produced by the process of this invention are triethyl boron ammonia, trimethyl boron dimethyl amine, triethenyl boron methyl amine, triethynyl boron trimethyl amine, triethynyl boron pyridine, tridecyl boron pyridine, triphenyl boron ammonia, dimethyl ethyl boron ammonia, diethyl phenyl boron ammonia, diethynyl methyl boron pyridine, ethenyl dimethyl boron dimethyl amine, diphenyl methyl boron methyl amine, methyl ethyl n-propyl boron ammonia, methyl ethenyl decyl boron pyridine, cyclohexyl methyl phenyl boron methyl amine, methyl ethenyl ethynyl boron ammonia, dimethyl fiuoro boron ammonia, diethenyl chloroboron methyl amine, diethynyl bromo ammonia, diphenyl methoxy boron methyl amine, methyl phenyl phenoxy boron ammonia, methyl dimethoxy boron ammonia, ethyl diethoxy boron pyridine, phenyl dipentoxy boron ammonia, hexyl diphenoxy boron methyl amine, isopropyl methoxy ethoxy boron dimethyl amine, o-methyl phenyl dimethoxy ammonia and the like.

The proportions employed in the process of this invention are such that stoichiometric requirements are fulfilled, that is, they are critical only in so far as the desired reaction product dictates. Thus, when the trisubstituted boron compound is desired, a reaction ratio of 3:1 organometallic to boron compound is employed. When the disubstituted derivative is desired, a 2:1 ratio is employed and likewise a 1:1 ratio when the monosubstituted derivative is desired. In order to obtain the benefits of this invention, it is preferred to maintain reaction proportions as near to the theoretical stoichiometry as feasible. However, up to about 5 percent excess of either reagent will not deter from the successful completion of the reaction. It should be noted, however, that during the addition it is necessary to maintain the boron compound in excess of the organometallic reactant and it is for this reason that the organometallic is added in a slow steady manner to the boron reactant.

The temperatures employed in the process of this invention are dependent upon the relative stability of amine complexed boron compound employed and upon the product obtained. Thus, for example, higher temperatures may be employed when boron tri-fluoride complexed with ammonia is reacted with the appropriate lower alkyl or alkynyl organometallic than when, for example, trimethyl amine is complexed with boron trifluoride and subsequently reacted With an organometallic such as tertiary butyl lithium. This phenomenom has many explanations, for example, the more sterically hindered amines such as dimethyl, phenyl methyl, diethyl and the like form less stable complexes with boron compounds than those amines which are relatively unhindered as, for example, ammonia or methyl amine. Likewise, the stability of the amine complex produced determines the upper limit of the temperature range of the reaction. With these considerations in mind, the process of this invention is generally conducted at temperatures between about 0 to 100 C., and preferably 0 to 50 C., dependent upon the relatively stability of the coordinating amine complex and of the products produced. In the following example, this observation will be more fully apparent.

Example 111 Into a reaction flask produced with means for heating, refluxing, continuous addition and stirring is added85 parts of boron trifluoride ammonia in 300 parts of pyridine. The mixture is heated to 100 C. and 114 parts of triethyl aluminum are added over a period of 15 minutes. Upon completion of the addition, the reaction mixture is refluxed at 100 C. for several minutes and then allowed to cool to room temperature following which the white solid containing mixture -is filtered. The filtrate is then distilled at atmospheric pressure so as to remove the last traces of solvent. Whereupon the product ethyl difluoroboron ammonia is obtained.

The solvents used in the process of this invention are not critical so long as the boron reactant has been com plexed with an appropriate amine. Thus, hydrocarbons, ethers and amines may be employed. When an amine solvent is employed the boron reactant may be introduced and complexed in situ. Furthermore, mixtures of solvents may be employed as evidenced by the process of Example I. Thus, for example, the organometallic can be dissolved in a hydrocarbon or ether, such as, benzene or absolute ether and introduced into a mixture comprising the boron reactant and a solvent, such as, pyridine.

The concentrations employed in the process of this invention are, additionally, not critical in so long as suitable contact is elfected between reactants. Thus, it is usually desirable to employ between about 15 to 40 percent by weight of the reaction mixture as solvent.

Reaction times vary between about 15 minutes to 2 hours being directly dependent upon the relative reactivities of the reactants employed. Thus, the relative bond strengths, reactant proportions, reaction temperature, concentrations all have a direct bearing on reaction rates, but in most cases the reaction should not require more than two hours for completion and, furthermore, in some cases, it is feasible that a reaction time of less than 15 minutes might be effective. The following examples more clearly illustrate the process of this invention.

Example IV The process of Example I is utilized with the exception that 279.4 parts of boron trichloride dimethyl amine is 6 reacted with 306.9 parts of di(1-propynyl)rnagnesium. The compound tri(1-propynyl)-boron complexed with dimethyl amine was obtained in substantial yields.

Example V The process of Example I is utilized with the exception that 162.2 parts of boron trichloride ethyl amine is reacted with 300 parts of phenyl sodium to obtain the compound tn'phenyl boron ethyl amine.

Example V1 Into a reaction flask provided with means for refluxing, heating, continuous addition and stirring is added 140.8 parts of n-propyl dichloro boron ammonia in 200 parts of ether. The mixture is heated to 50 C. and 97.8 parts of triethyl boron are added over a 20 minute period. Upon completion of the addition, the reaction mixture is refluxed at atmospheric pressure for several minutes and then allowed to cool to room temperature following which the solid material appearing in the reaction mixture is filtered. The filtrate is distilled at a pressure of 1 mm. so as to remove the last traces of solvent whereupon the product diethyl n-propyl boron ammonia is obtained in good yields.

Example VII Example VIII Into a reaction flask provided with means for stirring, refluxing, and continuous addition is added 172.8 parts of ethyl diethoxy boron diethyl amine in 250 parts of absolute ether. To the reaction mixture is added, over a period of 1 hour, 50.4 parts of sodium butyl aoetylide while refluxing the reaction mixture at atmospheric pressure. Solid impurities are removed from the reaction mixture by vacuum filtration and the filtrate is distilled at 1 mm. of pressure to remove the last traces of the ether solvent. Thus, the product ethyl di( butylethynyl)boron is obtained as the diethyl amine complex.

As disclosed in US. 2,234,581, the compounds produced in the process of this invention may be employed as oxidation inhibitors in mineral lubricating oils and greases where usage requires exposure to high temperatures in the presence of air or combustion gases. While the exact nature of these various compounds and the mechanisms by which they improve the lubricating oil are not readily understood, observation discloses a tendency to decrease sludging and thereby render those decompositions products formed under their influence freely soluble or at least dispersable in the oil, thus greatly diminishing any inherent precipitation tendencies. Furthermore, the alkynyl boron derivatives produced by the process of this invention are preferably utilized as high energy fuels.

This application is a division of our copending application, Serial No. 651,797, filed April 10, 1957, now US. Patent No. 2,961,443.

We claim:

1. A process which comprises reacting in the liquid phase of stable organometallic compound with an amine complex of a boron compound; the organo group of said organometallic being a hydrocarbon group of from 1 to about 10 carbon atoms and the metallic constituent of said organometallic being selected from the group consisting of sodium, lithium, potassium, magnesium, calcium, zinc, mercury, and aluminum; said amine complex having the formula wherein R is a hydrocarbon group of up to 16 carbon atoms, X is a radical selected from the group consisting of halogen, alkoxy of up to about 10 carbon atoms, aryloxy of up to about 10 carbon atoms, and alkenoxy of up to about 10 carbon atoms, A is a nitrogenous entity complexed with the boron atom and is selected from the group consisting of unsubstituted ammonia, ammonia in which the hydrogen is substituted only by one to three hydrocarbon moieties of up to 10 carbon atoms, pyridine, quinoline, piperidine, acridine and isoquinoline, and a is an integer from to 3, inclusive, and carrying out the reaction to form a new amine complex of a boron compound with a hydrocarbon radical from said organometallic compound, the reaction temperature being below that1 at which the new amine complex decomposes excessive y.

2. A process for preparing organoboron compounds which comprises reacting in the liquid phase at a temperature from 0 to 100 C. a stable organometallic compound with an amine complex of a boron compound; the organo group of said organometallic being selected from the group consisting of a lower alkyl and lower \alkynyl group and the metallic constituent of said organometallic being a group I-A metal; said amine complex having the formula wherein R is a hydrocarbon radical of l to carbon atoms, X is a halide, A is complexed with the boron atom and is a six-membered ring of five carbon atoms and one nitrogen atom with no ring substituents other than the carbon and hydrogen required to constitute polycyclic ring systems, and a is an integer from 0 to 3, inclusive.

3. A process for the preparation of an alkynyl boron amine complex which comprises reacting in the liquid phase at a temperature from 0 to 100 C., an alkali metal alkyne of up to 10 carbon atoms with a complex of a boron halide with an ammonia in which all three of the ammonia hydrogens are substituted by a hydrocarbon radical of up to 13 carbon atoms, said ammonia being a six-membered ring of five carbon atoms and one nitrogen atom with no ring substituents other than the carbon and hydrogen required to constitute polycyclic ring systems.

4, A process for the preparation of triethynyl boron pyridine which comprises reacting in the liquid phase at a temperature from 0 to C., sodium acetylide with the boron trifluoride pyridine complex.

5. A process for preparing organoboron compounds which comprises reacting in the liquid phase at a temperature from 0 to 100 C. a stable organometallic compound with an amine complex of a boron compound; the organo group of said organometallic being selected from the group consisting of a lower alkyl and lower alkynyl group and the metallic constituent of said organornetallic being a group I-A metal; said amine complex having the formula wherein R is a hydrocarbon radical of 1 to 10 carbon atoms, X is a halide, A is an ammonia in which the hydrogen is substituted only by l to 3 hydrocarbon moieties of up to 10 carbon atoms, and a is an integer from 1 to 3 inclusive.

References Cited in the file of this patent Lappert et al.: Chem. Reviews, vol. 56, pp. 1032 (1956).

Sazonova et al.: Chem. Abstracts, vol. 50, pp. 11339 (1956). 

1. A PROCESS WHICH COMPRISES REACTING IN THE LIQUID PHASE OF STABLE ORGANOMETALLIC COMPOUND WITH AN AMINE COMPLEX OF A BORON COMPOUND; THE ORGANO GROUP OF SAID ORGANOMETALLIC BEING A HYDROCARBON GROUP OF FROM 1 TO ABOUT 10 CARBON ATOMS AND THE METALLIC CONSTITUENT OF SAID ORGANOMETALLIC BEING SELECTED FROM THE GROUP CONSISTING OF SODIUM, LITHIUM, POTASSIUM, MAGNESIUM, CALCIUM, ZINC, MERCURY AND ALUMINUM; SAID AMINE COMPLEX HAVING THE FORMULA 